Production of valuable hydrocarbons



N. K. CHANEY v PRODUCTION OF VALUABLE HYDROCARBONS Filed July 22, 1938ken 7 Q? W Kl ENTOR.

ATTORNEY.

Patented Dec. 31, 1940 UETED STATES PATENT OFFICE.

CARB

ONS

Newcomb K. Chaney, Rose-Valley, Moylan, Pa.,

assignor to The United vGas Improvement Company, a corporation ofPennsylvania Application July 22, 1938, Serial No. 220,649

8 Claims. (01. 260-671) The present invention relates to thesimultaneous production of manufactured gas and valuable hydrocarbons,and relates more particularly to increasing the yield of certain of said6 hydrocarbons.

In the usual manufacture of oil gas or carburetted water gas, a step inthe process comprises cracking of crude petroleum oil or its less costlyportions, such as gas oil and residuum oil, under 10 conditions whichyield relatively large quantities of fixed or difilcultly condensiblegases, such as hydrogen, methane and ethylene together with othergaseous paraflines and olefines, and relatively small quantities of morereadily condensible hydrocarbons comprising tar, drip oil and lowertemperature condensates. Broadly stated the division between the gaseousand other products depends upon the severity of cracking and theseverity of condensation.

It has been proposed to modify the usual conditions of crackingtemperatures and time of contact and the temperature of condensation, toproduce andrecover smaller proportions of the original oil as gaseousproducts for distribution as fuel and larger proportions as condensatecontaining hydrocarbons more valuable for other uses.

Among the hydrocarbons so recoverable are saturated and unsaturatedcompounds such as benzene, toluene, xylene, naphthalene, anthracene.indene, styrene, methyl styrene, cyclopentadiene, butadiene, isoprene,piperylene, etc.

The usual gas manufacturing condensation down to atmospheric temperatureremoves from the gas practically all of the xylene, naphthalene,anthracene, indene, styrene, and methyl styrene, a small part of thebenzene, and possibly half of the toluene. For the recovery of theremainder of the benzene and toluene and for the recovery of the dienesmuch lower temperatures of condensation than usually employed in gasmanufacture are required.

Among the aromatic hydrocarbons noted above, the alkylated aromatics arein general more vaiuable than the benzene. This is particularly true ofthe toluene, xylene and styrene.

The principal object of the present invention is to provide a method ofincreasing the yield of alkylated aromatic hydrocarbons relative to theyield of benzene.

Other features of the invention reside in the steps, combinations ofsteps .and sequences of steps, all of which together with other featureswill become more apparent to persons skilled in the art as thespecification proceeds and upon reference to the drawing -which shows inelevation and partly in section, a conventional three shell carburettedwater gas set chosen for illustration.

Referring more particularly to the drawing, I 5 indicates a generator, 2a carburetter, 3 a super heater and 4 a wash box.

Generator I is illustrated as having a fuel bed 5, an up run air blastsupply 6, and an up run steam supply I. 10

Superheater 3 is shown with a down run steam supply 8.

Generator l is provided at its top with an offtake 9 leading to the topof the carburetter 2, and carburetter 2 is provided at its base with an15 off-take 10, leading to the base of the superv heater 3.

Superheater 3 is shown with a stack valve II and a gas cit-take I 2, thelatter leading to wash box 4 through valve l3. 20

Generator I has a gas off-take I4 at its base provided with valve I5.Gas off-take I4 leads to wash box 4.

Wash box 4 is shown with the conventional gas The apparatus so farparticularly described is entirely conventional in character. Any othergas making equipment employing a run with oil might have beensubstituted for the purposes of describing the invention. 30

The operation of the apparatus will be de-= scribed with a conventionalcycle.

The fuel bed 5 is blasted with air supplied at 6. This raises thetemperature of the fuel bed and generates producer gas which is burnedas 35 it flows through the set by secondary air introduced at I! throughpipe l8 controlled by valve I9.

The hot blast gases pass down through the carburetter 2 and up throughsuperheater 3 rais- 40 ing the temperature-of the carburetter andsuperheater and storing heat therein, and finally escape through stackvalve i l.

After the air blasting operation the set is purged of blast gases bysteam admitted at I, whereupon 4.5 stack valve II is closed, valve I3 isopened and an up run is made with steam supplied at the same point. Theblue water gas thus made passes through carburetter 2, superheater 3,wash box 4, and flows out through ofi-take I6. 50

During this up run with steam petroleum oil is introduced into the setfor cracking and fixing in the carburetter and superheater.

Although-the point of introduction of petroleum oil may vary inditferent gas making equipment,

- mospheric temperature.

a light oil by fractional distillation.

for convenience in description I have illustrated an oil spray 2| at thetop of carburetter 2.

Irrespective of the construction of the inside of the carburetter, whichmay vary widely in different types of apparatus, it is customary to havea. substantial part of this petroleum oil come directly into contactwith the heated surfaces,

whether they be of checkerbrick, or of other construction or comprisemerely the side walls. However, whether coming into contact with theheated surfaces or not this oil is subjected to the temperatures of thecarburetter and superheater as it is carried along by the stream of bluewater gas, and is cracked into gas, coke, tar, drip oil and othercondensates. The coke is usually deposited in the carburetter andsuperheater and the condensates. are usually carried out .of thesuperheater and are condensed at the wash box and cycle might besubstituted.

After passing through the ofi-take it the gas usually goes to a reliefholder and from thence through water cooled condensers to the purifiers.

for the removal of hydrogen sulfide, and thence to storage holders forrelease to the distribution system.

The wash box 6 in which the gas comes in contact with water, and thewater cooled con' densers cool the gas down to approximately at- The tarand oil condensed out in these vessels comprises a residual tar fractionboiling above 300 C., a dead oil fraction boiling between 200 C. and 300C., and a light oil fraction boiling up to 200 C. and containingpractically all of the styrene, indene, and xylene, possible, half ormore of the toluene and some of the benzene and other miscellaneoushydrocarbons or benzol forerunnings. The individual compounds may berecovered from the Usual carburetted water gas practice does not carrythe condensation further. However, if after purification the gas iscooled by stages to approximately 65 C., the remainder of the benzeneand toluene, as well as the dienes, cyclopentadiene, butadiene, isopreneand piperylene, may be condensed out and recovered separately byfractional distillation.

In the normal production of aromatics from the cracking of petroleumoils, the reaction is supposed to proceed generally as follows:

paraffines olefines and dioleflnes cyclic olefines and naphthenesaromatics Normally, the production of benzene is relatively highcompared to the production of toluene and the higher individual aromaticderivatives such as thexylenes, styrene, indene, etc. The production ofthe alkylated aromatics probably proceeds at least in substantial part,by union of benzene with free alkyl radicals as troleum oil.

benzene+free radicals alkylated aromatics In the normal course of thereactions, through the set or other cracking apparatus, the productionof benzene is a delayed reaction occurring in the later stages of thecracking operation. On the other: hand, the production of free radicalsoccurs largely in the initial stages of the cracking operation.

By increasing the concentration of benzene above that caused bythe'concurrent formation of benzene in the petroleum oil crackingoperation in its early stages, a greater benzene concentration isprovided at the time of maximum free radical formation and the abovereaction of benzene with free radicals to form alkylated aromatics isfavored.-

Also the presence of an increased benzene concentration above the normalequilibrium concentration in the later stages of the cracking operationtends to oppose the formation of additional benzene by mass action. Thistends to suppress the breaking up of alkylated aromatics formed in theearlier stages to form benzene in the later stages of the crackingoperation.

Whether the theory above set forth be correct or not, I have found thatincreasing the benzene concentration above that produced by the normalformation. of benzene from the oil in the early stages of the crackingoperation favors an .increase in the yield of alkylated aromatics Thusthe increased concentration of benzene may be secured by introducingadditional ben-' acne into the cracking chamber during the cracking ofthe oil.

All or part of the benzene may be separated I such as the carburetterand superheater above.

described, may be widely varied with different cycles and methods ofoperation, it may not be desirable to introduce the benzene at the pointof admission of the petroleum oil, as the zone of maximum free radicalproduction will necessarily vary with the variation in temperaturedistribution.

The, benzene recycled need not be refined benzene, but may be a crudebenzol containing cut from the high or low temperature condensate or amixture of crude cuts from the condensates. In fact, I have found that avery materially increased yield of styrene, a very valuable alkylatcdaromatic can be secured by recycling light cil containing considerablequantities of toluene, xylene, styrene, indene and residual tar, inaddition to benzene. For the purpose of the claims benzol is defined asa mixture of hydrocarbons in which benzene is the principal constituent.

Benzene from any other sourcemay be employed if desirable.

Benzene may'be recycled by separating all or part of the benzene andadding it to the re sidual or stripped gas rich in ethylene andpropylene, after condensation of the valuable but thermally unstabledienes, and recycling the mixture of benzene and residual or strippedgas through the cracking apparatus with the pe- III The conventionalcarburetted water gas apparatus and cycle earlier described were givenmerely forconvenient illustration of apparatus and process adapted foruse with my invention, and are subject to vary wide modifications. Itmay bepreferable to curtail sharply or to omit the production of bluewater gas, employing the fuel bed merely as a means of heating thecarburetter and superheater. In such case, in the absence of the bluewater gas and excess steam cracking atmosphere, it is desirable to admitsteam or other diluent to the carburetter with the petroleum oil toreduce the partial pressures of the vapors and products of cracking.This steam may 'beadmitted through a supply means such as 23. otherconvenient means of heating'such as an oil, tar, or gas burner inwhichcase it is also desirable to admit steam or other diluent with the oil.The above modifications are merely il lustrative. The invention isapplicableto any cyclic process in which petroleum oil is thermallycracked under temperature and contact conditions yielding relativelyfixed gas and more readily condensible hydrocarbons including benzeneand alkylated aromatics.

As an example of increased yields of alkylated aromatic hydrocarbonsrelative to the yield of benzene in the performance of the invention inapparatus of the character described, the following may be given.

A mixture of Texas Coastal crude oil and refined benzol, in proportionsof 2 parts 011 and 1 part benzol by volume, was cracked under the sameconditions of temperature and contact as a control employing 100% TexasCoastal crude oil.

In each case steam was admitted with the material cracked, and the setmaintained at the average temperature also given below in a table whichshows the yields of benzene and alkylatedaromatics.

Tvlvo parts by vo ume eras Coastal crude gg g oil-one part crud: byvolume 1 benzol Average temperature .'F. 1484 1490 Styrene .lbs./gal. ofoil 0.103 0.073 ..do.... 0177 0.086 ..d0 -0.065 0.518 11 d0 0.397 0.362Solvent naphtha ..do.. 0. 348 0.235 Residual tar "do" 1. 375 1. 654Total alkylated aromatics (solvent naphtha calculated as xylene) 1.0730.823

As above stated, I have further found that the yield of styrene, a veryvaluable alkylated hydrocarbon, may be very materially increased byrecycling light oil separated from the atmospheric temperaturecondensate from the gas and containing benzene, toluene, a smallerquantity of xylene and still smaller quantities of indene and styrene.

As an example, light oil containing approxi mately 43.1% benzene, 31.5%toluene, 4.6% xylene 1.27% indene, 0.77% styrene and 3.3%

' residual tar was mixed with a Texas Coastal crude oil in proportionsof two parts of crude oil to one part light oil by volume.

The mixture was sprayed into the carburetter of a conventional threeshell water gas set, at a rate of approximately 3 gallons per minutewith steam at the rate of 22.5 pounds per minute.

Temperatures taken at the top and middle of the carburetter and base,middle and top of the su- Also the fuel bed may be replaced by any vquire.

I claim:

1. In a cyclic process for making combustible gas which when practicedin a gas-making set includes in the cycle internally preheating saidgas-making set by passage of hot blast gases therethrough and agas-making run involving the introduction of petroleum oil into said setfor vaporization and cracking, the step of increasing the yield ofvaluable hydrocarbons including alkylated aromatic hydrocarbons whichcomprises introducing benzene into said gasmaking set during theintroduction of said petroleum oil.

2. In a cyclic process for making combustible gas which as practiced ina gas-making set includes in the cycle internally preheating saidgas-making set and a gas-making run involving the vapor phase crackingof petroleum oil therein, the step of increasing the yield of valuable'hydrocarbons including alkylated aromatic hydrocarbons which comprisesintroducing benzene into said gas-making set in addition to saidpetroleum oil during said vapor phase cracking of said petroleum oil.

3. In a cyclic process for making combustible gas which as practiced ina gas-making set includes in the cycle internally preheating saidgas-making set and a gas-making run involving the vapor phase crackingof petroleum oil therein in the presence of diluent gas, the step ofincreasing'the yield of valuable hydrocarbons including alkylatedaromatic hydrocarbons which comprises introducing benzene into saidgasmaking set in addition to said petroleum oil during said vapor phasecracking of said petroleum oil in the presence of said diluent gas.

4. In a cyclic process for making combustible gas which as practiced ina gas-making set includes in the cycle internally preheating saidgas-making set and a gas-making run involving the vapor phase crackingof petroleum oil therein in the presence of steam, the step ofincreasing the yield of valuable hydrocarbons including alkylatedaromatic hydrocarbons which comprises introducing benzene into saidgas-making set in addition to said petroleum oil during said vapor phasecracking of said petroleum oil in the presence of said steam.

5. In a cyclic process for making combustible gas which as practiced ina gas-making set includes in the cycle internally preheating saidgas-making set and a gas-making runinvolving the vapor phasecracking ofpetroleum oil therein, the step of increasing the yield of valuablehydrocarbons includingalkylated aromatic hydrocarbons which comprisesintroducing benzol into'saicl gas-making set in addition to said pe-'troleum oil during said vapor phase cracking of said petroleum oil.

6. The process of claim 5 wherein after the process is in operation thebenzol introduced into said gas-making set in addition to said petroleumoil isobtained by separation from the products of said vapor phasecracking or said petroleum oil.

7. In a cyclic process for making combustible gas which as practiced ina gas-making set includes in the cycle internally preheating saidgas-making set and a gas-making run involving the vapor phase crackingoi petroleum oil therein, the step of increasing the yield of styrenewhich comprises introducing benzene into said gas-making set in additionto said petroleum oil during said vapor phase cracking of said petroleumoil.

